1. Field of the Invention
The present invention relates to a disk drive, and more particularly, to a filtering apparatus for a disk drive to filter foreign materials in the disk drive.
2. Description of Related Art
Hard disk drives (HDDs) as data storage devices for a computer reproduce or record data with respect to a disk by using a read/write head. In the hard disk drive, the read/write head reproduces or records data while being moved by an actuator to a desired position in a state of being lifted to a predetermined height from a recording surface of the rotating disk.
FIG. 1 is a plan view illustrating the structure of a conventional 2.5 inch hard disk drive. FIG. 2 is a magnified perspective view illustrating a suspension portion of an actuator and a ramp shown in FIG. 1.
Referring to FIGS. 1 and 2, the hard disk drive includes a spindle motor 12 installed on a base member 10, at least one disk 20 fixed to the spindle motor 12, and an actuator 30 to move a read/write head (not shown) for reproducing and recording data to a specified position on the disk 20. The actuator 30 includes a swing arm 32 rotatably coupled to a pivot bearing 31 installed on the base member 10, a suspension 33 installed at one end portion of the swing arm 32 and supporting a slider 34, where the read/write head is mounted, to be elastically biased toward a surface of the disk 20, and a voice coil motor (VCM) to rotate the swing arm 32. The voice coil motor includes a VCM coil 36 coupled to the other end portion of the swing arm 32, a lower yoke 37 installed under the VCM coil 36, and a magnet 38 attached to an upper surface of the lower yoke 37. Although not shown in the drawing, the voice coil motor may include an upper yoke installed above the VCM coil 36 and a magnet attached to a lower surface of the upper yoke.
The voice coil motor having the above structure is controlled by a servo control system and rotates the swing arm 32 in a direction according to the Fleming's left hand rule by an interaction between current applied to the VCM coil 36 and a magnetic field generated by the magnet 38. When the hard disk drive is turned on and the disk 20 is rotated in a direction D, the voice coil motor rotates the swing arm 32 counterclockwise, i.e., in a direction A, so that the read/write head is moved over the recording surface of the disk 20. The slider 34 is lifted to a predetermined height from the surface of the disk 20 by a lift force generated by the rotation of the disk 20. In this state, the read/write head mounted on the slider 34 reproduces or records data with respect to the recording surface of the disk 20.
When the hard disk drive is not in operation, that is, the rotation of the disk 20 is stopped, the read/write head is parked at a position out of the recording surface of the disk 20 so that the read/write head does not collide with the recording surface of the disk 20. The head parking system can be classified into a contact start stop (CSS) method and a ramp loading method. In the CSS method, a parking zone where data is not recorded is provided at an inner circumferential side of the disk 20 and the read/write head is parked in the parking zone in a contact manner. However, in a head parking system in the CSS method, since the parking zone is provided at the inner circumferential side of the disk 20, a space for storing data is lessened. Thus, to meet the recent trend toward a higher data recording density, a ramp loading type head parking system which can secure a wider data storage space is widely adopted.
According to the ramp loading method, a ramp 40 is installed outside the disk 20 so that the read/write head is parked on the ramp 40. To this end, an end-tab 35 which contacts and supports a support surface 41 of the ramp 40 is extended from an end portion of the suspension 33. The end-tab 35 generally has a bulge toward the support surface 41 to reduce a contact area between the end-tab 35 and the support surface 41 of the ramp 40.
When the hard disk drive is turned off so that the rotation of the disk 20 is stopped, the voice coil motor rotates the swing arm 32 clockwise in a direction B. Accordingly, the end-tab 35 is unloaded from the disk 20 and moved over the support surface 41 of the ramp 40. When the hard disk drive is turned on and the disk 20 starts to rotate, the end-tab 35 is moved out of the support surface 41 of the ramp 40 and loaded over the disk 20, by the rotation of the swing arm 32.
When the read/write head is parked on the ramp 40, the read/write head may escape from the ramp 40 and move toward a recording surface of the disk 20 as the actuator 30 is arbitrarily moved by external impacts or vibrations applied to the disk drive. In this case, the read/write head contacts the recording surface of the disk 20 and the read/write head and the recording surface may be damaged. Thus, an actuator latch 50 is provided to lock the actuator 30 at a particular position so as not to be moved arbitrarily when the rotation of the disk 20 stops and the read/write head is parked on the ramp 40.
A flexible printed circuit (FPC) bracket 60 to connect a flexible printed circuit 62 connected to the actuator 30 to a printed circuit board (not shown) arranged on a lower surface of the base member 10 is installed at one corner of the base member 10.
In the hard disk drive having the above structure, foreign materials such as particles or gas are generated in the following situation.
When the end-tab 35 is moved toward the disk 20 or over the support surface 41 of the ramp 40, sliding friction occurs between the end-tab 35 and the support surface 41 of the ramp 40. When such friction is repeated, the support surface 41 of the ramp 40 which is generally formed of plastic is worn so that particles are generated. FIG. 3 shows particles adhering to and around the end-tab 35. In addition, when the read/write head is lifted over the surface of the disk 20, the read/write head collides with the surface of the disk 20 by the external impacts or vibrations so that particles are generated due to friction and wear between the read/write head and the disk 20.
Also, in the hard disk drive, there are parts which are electrodeposition coated or nickel coated and parts such as a VCM coil 36 coupling portion of the actuator 30 and the ramp 40 which are formed of plastic. In a burn-in step of servo compensation, defect free, and head performance check, or after the disk drive is driven for a time, the temperature of the disk drive becomes high. In the high temperature state, gas is generated from the above parts. While moving according to the principle of the Brownian movement, molecules of the gas cause chemical reactions or collide with one another so that particles having a size of several hundreds nanometers are generated.
The particles flow inside the hard disk drive along the airflow caused by the rotation of the disk 20. The size of the flowing particle are various from several nanometers to several hundred nanometers. A particle which is greater than an interval (space) between the read/write head and the disk 20, that is, a flying height of the read/write head, collides with the read/write head to change the posture of the read/write head. Accordingly, the read/write head contacts the disk 20 and scratches the recording surface of the disk 20, which damages the disk and distorts a magnetic signal therefrom. In addition, the collision between the particle and the read/write head may damage a read/write sensor of the read/write head. A particle which is smaller than the flying height may intrude between the read/write head and the surface of the disk 20 so that the read/write head is damaged or scratches are made on the surface of the disk 20.
Hard disk drives are being developed to be ultra-light and compact and have a high capacity. To meet these criteria, the track per inch (TPI) is remarkably increased to increase a storage capacity of a disk while the flying height of the read/write head is decreasing. As a result, the head can be easily damaged by even smaller particles and the magnetic signal on the disk surface can be easily damaged by even smaller scratches.
Thus, to prevent the above problems, foreign materials such as particles or gas generated in the disk drive need to be collected and removed. Conventionally, as shown in FIG. 1, a circulation filter 70 is arranged in a corner of the base member 10 to filter foreign materials such as particles included in air flowing inside the disk drive. However, the circulation filter 70 arranged as above does not provide a satisfactory filtering effect as described below.
FIG. 4 shows the result of simulation of the distribution of speed of particles flowing on and around the surface of a rotating disk in the conventional 2.5 inch hard disk drive shown in FIG. 1.
Referring to FIG. 4, as the disk rotates, airflow is generated in the disk drive and particles in the disk drive is moved along with the air flow. The flowing speed of the particles is almost proportional to the flow speed of the air. Accordingly, as shown in the drawing, on the disk surface, the flow speed of the particles is faster at a position close to the outer circumference of the disk while the flow speed of the particles is slower at a position close to the inner circumference of the disk. However, as shown in FIG. 4, the airflow hardly exists in an area R1 outside the disk where the conventional circulation filter 70 is arranged so that the particles hardly flow toward the circulation filter 70. Therefore, the conventional circulation filter hardly functions to collect particles in the area R1.